1. Field of the Invention
This invention relates to face detection.
2. Description of the Prior Art
Many human-face detection algorithms have been proposed in the literature, including the use of so-called eigenfaces, face template matching, deformable template matching or neural network classification. None of these is perfect, and each generally has associated advantages and disadvantages. None gives an absolutely reliable indication that an image contains a face; on the contrary, they are all based upon a probabilistic assessment, based on a mathematical analysis of the image, of whether the image has at least a certain likelihood of containing a face. Depending on their application, the algorithms generally have the threshold likelihood value set quite high, to try to avoid false detections of faces.
In any sort of block-based analysis of a possible face, or an analysis involving a comparison between the possible face and some pre-derived data indicative of the presence of a face, there is a possibility that the algorithm will be confused by an image region which, while possibly looking nothing like a face, may possess certain image attributes to pass the comparison test. Such a region may then be assigned a high probability of containing a face, and can lead to a false-positive face detection.
It is a constant aim in this technical field to improve the reliability of face detection, including reducing the occurrence of false-positive detections.